The invention relates to an electronic power overload protection circuit adapted to limit the output power of a signal amplifier with the help of a sensing element which forms a part of a feedback circuit for said amplifier and which becomes conductive when a predetermined maximum output power threshold has been reached.
Such a protection circuit for push-pull amplifier output transistors is known from the published European patent application 0058005 in which the sensing element is a transistor so associated to the output transistor that the square of its collector current is a linear function of the output transistor collector current and of the product of the latter and the collector-emitter voltage of the output transistor. The protection operation start level can be selected by modifying the parameters of the sensing and other associated transistors and resistors but the protection circuit is always active and thus continuously consumes power.